Flashlights are conveniently sized battery powered portable light sources, which provide the user with a source of illumination. Said illumination could be white light or light of a specific color, or even light outside the visible range of wavelengths, such as ultra violet or infrared radiation. The “color” or wave length of the light will depend on the nature of the light source or light sources used in the flashlight. Typical light sources or “lamps” are tungsten filament lamps, ARC lamps, light emitting diode (LED) lamps, lasers, and any other emitter.
Because of the general nature of flashlights and their wide range of applications, it is very desirable for a flashlight to be able to emit, at the user's direction, different levels of light output, and/or different colors or wavelengths of light. This can be accomplished using multiple light sources or a single light source, which can be adjusted to provide different levels of light output.
Multiple lamp flashlights have proven effective to provide dual light levels, and dual color choices. An examples of such prior art systems is described in U.S. Pat. No. 5,629,105 to Matthews, incorporated herein by reference, and which describes the use of a main tungsten filament lamp at the focus of a parabolic reflector, with a separately-switched second lamp protruding or shining through the reflector at a point offset to the side of the main lamp. The second lamp may be an LED of any selected color, and one successful version of this flashlight has an array of three such LED lamps, each with an encapsulated body having a curved front lens surface that serves to collimate the emitted light.
The use of a parabolic reflector is reasonably effective for tungsten lamps having a filament emitting light in a nearly omnidirectional pattern, because it efficiently captures the bulk of the light emitted laterally and somewhat rearwardly. In contrast, a reflector is less efficient for LED light sources that emit the bulk of their light in a generally forward direction, with less emitted laterally, and minimal rearward emissions. A conventional reflector system allows the forward cone of emissions that does not strike the reflector to illuminate a broad circle defined by the shadow of the forward rim of the flashlight housing. For a typical configuration, this unfocused direct illumination represents about 20–30% of the output of the tungsten lamp, leaving an appreciable portion of the lamps emission to be reflected and focused to a bright spot. In contrast, with an LED lamp suited for primary flashlight illumination, the same reflector geometry may allow up to 60% of illumination to go unfocused, providing a central spot of inadequate brightness.